1. Field of the Invention
The present invention relates to a light diffusing plate which has anisotropy in the scattering of linearly polarized light, is highly effective in diffusing the directions of the scattering thereof, and is suitable for use in, e.g., improving the perceptibility, brightness, and other performances of liquid-crystal displays and the like. This invention further relates to an optical element employing the light diffusing plate.
The present application is based on Japanese Patent Application No. Hei. 10-376394 which is incorporated herein by reference.
2. Description of the Related Art
Conventionally known light diffusing plates which comprise a matrix and, dispersedly contained therein, regions having anisotropy in refractive index and which are anisotropic with respect to the scattering of linearly polarized light include a diffusing plate comprising a combination of a thermoplastic resin and a low-molecular liquid crystal, one comprising a combination of a low-molecular liquid crystal and a photocrosslinkable low-molecular liquid crystal, and one comprising a combination of poly(vinyl alcohol) and a low-molecular liquid crystal (see U.S. Pat. No. 2,123,901, WO 87/01822, EP 0506176, and JP-A-9-274108). (The term “JP-A” as used herein means an “unexamined published Japanese patent application”.)
The above light diffusing plates are intended, for example, to supply linearly polarized light in such a state as not to be readily absorbed by a polarizing plate to thereby reduce absorption loss and thus improve the brightness of liquid-crystal displays. Such light diffusing plates may be expected to eliminate problems of a conventional system for absorption loss reduction comprising a cholesteric liquid-crystal layer and a quarter-wavelength plate. These problems are that the large wavelength dependence of the cholesteric liquid crystal causes coloration of, in particular, obliquetransmitted light, and that the conventional system is inapplicable to reflection type liquid-crystal displays or the like.
However, the conventional light diffusing plates described above are unsuitable for practical use, for example, because they are difficult to produce and because when applied to liquid-crystal displays or the like, the diffusing plates have poor handleability and poor stability of functions.